Comprehensive analysis of the effect of oxyfuel atmospheres on solid fuel combustion using Large Eddy Simulations

Coupling oxyfuel combustion with carbon capture and storage (CCS) technologies offers a promising near-term solution for cleaner power generation. For understanding the effects of oxyfuel combustion versus air combustion, this study employs a Large Eddy Simulation (LES) approach coupled with advanced radiation and solid fuel conversion models, using six-dimensional flamelet tabulation and Lagrangian particle tracking. The framework is applied to a lab-scale, swirl-stabilized, methane-assisted, solid fuel combustion chamber operated with pulverized Rhenish Lignite. Three single-phase methane flames and three comparable multiphase methane/coal flames are investigated. In both single-phase and multiphase conditions air serves as the reference oxidizer. Two additional oxyfuel operation modes, both with 33 % vol. O₂, are analyzed: one maintaining constant thermal power and the other maintaining constant feed flow rates, each compared to the respective single-phase or multiphase air case. The simulation results are compared to a unique set of experimental data, covering an exceptionally wide range of operating points measured with minimally invasive laser-based techniques. The simulation results are found to capture key differences between operating conditions. A weaker swirl stabilization is observed in same-power multiphase oxyfuel condition, explained by the drag force of particles and lower gas velocities. Furthermore, particle size and residence time distributions within the flame are calculated, revealing a higher tendency for particles in the intermediate size range to escape the air flame compared to oxyfuel flames.